Part Proliferation, Why it takes away your competitive edge? Part 3: Fasteners

Last Blog we looked at ways to cleanup parts off the inventory as well as the ripple effect this cleanup may have on your bottom line. In this Blog we will look at fasteners. They can have an immediate impact on design, supply, and manufacturing total cost when standardized.

Influence of Fastener,

Fasteners have been around for centuries; in all shapes or forms and materials, for all kind of applications. Typically, the application is what drive the selection of a type of fastener, the environment is what drives the material selection. There are however other factors that will influence the selection of a fastener: The tooling available on the factory floor and method used (robots, auto-feed screwdrivers, manual installation etc.) to install the fastener will also have a predominant influence on the selection, and these factors are often forgotten, only to be figured out during critical design reviews when 90% of the manufacturing cost has been committed by design.  Although fasteners are typically the smallest and the least expensive components in an assembly, if they are not properly selected and standardized, they can prohibitively drive up the cost of assembly, therefore compromising the competitivity of the product on the market.

Consideration in selecting fasteners,

Companies should develop their own considerations based on their manufacturing process and products that ultimately leads to the selection of a fastener or group of fasteners for a given application. One cannot arbitrarily select a fastening system without answering (at least) the very basic questions listed hereafter and incorporate the answers in the design. Selecting the fastening system for a given product early in the design process will lead to a conscious decision that will have an impact on the committed cost of manufacturing:

Application: Aircraft, Marine, Space, Bridge, Building, Furniture, Electronics etc...

• Load Case: Tension, Shear, Fatigue…
• Limitations: Structural, Non-Structural, Fatigue, Creep, Secondary Stress...
• Environment: Corrosive, Liquid, Space, Temperature, Salty...
• Type of joint: Fastened, Bonded, Permanent, Structural, Non-Structural...
• Joint Material: Metal, Plastics, Rubber, Concrete, Wood, Composites, Dissimilar materials...
• Number of fastening components: Screw or bolt only, washer needed, nut needed, Inserts, nut plates, self tapping...
• Installation methods: Manual, Mechanical, Quick Turn, Robotics...
• Tooling: Auto-feed, manual, robot, jigs, special tools, power tools, Access...
• Access: From top, from bottom...
• Security/Safety: Lock-wire, lock features, vibration, loosening, fatigue...
• Fastener hole Type: drilled, tapped, self-tapping…
• Fit: Clearance, loose, Press-fit...
• Head Design: Flat, Hex, Fillister, etc….
• Drive: Slotted, Hex, Philips, Robertson, Hex Socket...
• Size: Diameter and length...
• Availability: Stock, COTS, Custom...
• Fastener initiatives

Initiatives in fastener standardization will have a significant impact on total cost. Obviously the least expensive fastening system is no fastener at all, but this is another subject. The easiest way to limit fastener types is to impose a limitation on designers and educate them on what is preferred from a manufacturing point of view; the Designers are the ones selecting the fasteners. One easy way to do this, is by creating boards showing the preferred and accepted fasteners, but with today’s CAD systems, coupled with Fastener managing Systems such as SynchroFit – Vistagy and Cenit AG,  the preferred fasteners and what is common stock can be modeled and kept in a library that is linked to the Master BOM, giving full visibility to designers of what is available at all time.  In fact, Designers should always design with what is available on the factory floor. Any new fastener introduced to the factory floor should be thoroughly analyzed as the impact on factory activities can be significant.

The Ripple Effect

Minimizing the types of fastener in inventory will maximize the buying power, therefore lower cost via an economy of scale. The effort and cost to create a library and database will pay for itself in time saved in engineering, but mostly in time saved on the factory floor.  Further initiatives should thrive at designing for the least number of fastener type, and even to design for no fasteners when possible.

Closing Comment

It is a known fact that fastener types have proliferated in product development, to the point where the true selection criteria's are becoming blurred.  Understanding the influence of fasteners and how we select them will lead to significant savings on the total cost of product development. It is worth putting the effort to create initiatives that will lead to a more judicious use and a better selection of fasteners, while reducing cost.